1. Field of the Invention
The present invention relates to an electronic device system including an electronic device, such as a portable computer, employing a pen-input system and an expansion station for expanding a function of the electronic device.
2. Description of the Related Art
A kind of book-type portable computer is known, to which information is input through a handwriting input device using a pressure-sensitive tablet and a stylus pen. The computer employing the pen input system includes a flat case, having an upper surface on which an input surface of the tablet is formed. The case of this kind of computer is designed to be compact, since the portability is more important in this computer as compared to a general portable computer having a keyboard. Since the compact case has little space inside, it cannot incorporate various function devices, such as a large-capacity memory device.
For this reason, the pen-input type computer has a plurality of connectors or ports on the back surface of the case to expand the function of the computer. Recently, there is a great demand for connecting a pen-input type computer to a hard disk drive, a CD-ROM drive, or an expansion station having a number of expansion ports, thereby adding a new function to the computer.
In the pen-input type computer, however, since the input surface also serves as a display for displaying figures or letters, the computer does not comprise a display unit as used in the conventional book-type or lap top computers. Therefore, when the computer is to be connected to the expansion station, if the case of the computer is placed so as to face upward on the upper surface of the expansion station, the input surface of the computer is inevitably horizontal. In this state, the visibility of the input surface may be degraded or information cannot be efficiently input by the stylus pen.
Further, since an advantage of the pen-input type computer is convenience in portability, even when it is connected to the expansion station, it is preferable that the connection be released easily. In this case, however, when a signal is transmitted between the computer and the expansion station, the computer may be unexpectedly removed from the expansion station. As a result, the computer is electrically disconnected from the expansion station, and important information may be deleted or the computer may malfunction.
To cope with this problem, it is proposed to provide the expansion station with a locking device for disconnectably locking the computer. However, with this constitution, the locking device must be operated to the locking position, after the computer is connected to the expansion station. In addition, to remove the computer from the expansion station, it is necessary that the lock of the computer should be released in advance. For this reason, it takes a considerable time to connect or disconnect the computer to or from the expansion station.